DESCRIPTION

These functions are glibc-specific.
An argz vector is a pointer to a character buffer together with a
length, see argz_add(3). An envz vector is a special argz vector,
namely one where the strings have the form "name=value". Everything
after the first '=' is considered to be the value. If there is no '=',
the value is taken to be NULL. (While the value in case of a trailing
'=' is the empty string "".)
These functions are for handling envz vectors.
envz_add() adds the string "name=value" (in case value is non-NULL) or
"name" (in case value is NULL) to the envz vector (*envz, *envz_len)
and updates *envz and *envz_len. If an entry with the same name
existed, it is removed.
envz_entry() looks for name in the envz vector (envz, envz_len) and
returns the entry if found, or NULL if not.
envz_get() looks for name in the envz vector (envz, envz_len) and
returns the value if found, or NULL if not. (Note that the value can
also be NULL, namely when there is an entry for name without '=' sign.)
envz_merge() adds each entry in envz2 to *envz, as if with envz_add().
If override is true, then values in envz2 will supersede those with the
same name in *envz, otherwise not.
envz_remove() removes the entry for name from (*envz, *envz_len) if
there was one.
envz_strip() removes all entries with value NULL.